The invention relates to a device for actuating a gas exchange valve of an internal combustion engine with a pivot armature actuated by electromagnetic drive units.
DE 196 28 860 A1 discloses a generic device for actuating a gas exchange valve of an internal combustion engine. This device, designed as an electromagnetic actuator, comprises two electromagnetic units, of which one acts in the opening direction and one in the closing direction of the valve. By means of the two electromagnetic units, a pivoting armature can be actuated, which is operatively connected to the gas exchange valve via a valve stem. The pivoting armature and the two electromagnetic units are arranged in a common housing. The pivoting armature is mounted in the housing via a rotary shaft.
It is the object of the present invention to provide a device for actuating a gas exchange valve of an internal combustion engine, which can easily be adjusted so that a minimal air gap remains when the pivoting armature is pivoted towards one of the electromagnetic units.
In a device for actuating at least one gas exchange valve of an internal combustion engine, comprising at least one pivoting armature, which is operatively connected to the gas exchange valve, and at least one first and at least one second electromagnetic unit, which serve for actuating the pivoting armature, the pivoting armature is included in a first functional group together with an armature housing and the two electromagnetic units are included in a second and third functional groups and the functional groups are inter-connected by connection means.
The division of the device into functional groups makes it possible first to assemble the components of the respective functional group and, before the connection of the functional group, to subject the components to machining, in particular precision machining, such as grinding, fine milling, etc., so that distortions which may possibly occur during the assembly of the respective components are eliminated. The active surfaces of the individual functional groups, after their assembly, are freely accessible to an extent such that they can be subjected to machining. In particular, active surfaces of the respective functional groups, that is to say the active surfaces of the pivoting armature and the respective active surfaces, usually formed by a yoke, of one of the two electromagnetic units, can be subjected to machining in such a way that, after the inter-connection of the functional groups, and in a corresponding pivot position of the pivoting armature, there is no, or only a minimal, air gap between these active surfaces. Minimal tolerances can be achieved, for example, by grinding.
Furthermore, it is possible, during machining, to apply deformations to which the respective functional group is subjected when the device is in operation, so that, when the device is in operation, in a corresponding position of the pivoting armature, a clearance, which is constant over the active surfaces or no clearance at all, is present between the respective active surfaces.
The connection means may serve at the same time for connecting the functional groups to one another and for fastening the device, for example, to an actuator carrier or a cylinder head.
It is possible, for example, that the pivoting armature and one of the electromagnetic units are part of the first functional unit and the other electromagnetic group is part of the second functional group. However, in order that active surfaces are oriented optimally in relation to one another both in the opening position of the pivoting armature and in the closing position of the pivoting armature, the device according to the invention advantageously comprises a third functional group which is assigned to one of the two electromagnetic units and which is connected to the first functional group via connection means. It is thereby possible to subject both the opening-side and the closing-side active surfaces to machining, in particular precision machining, before the connection of the functional groups.
According to one advantageous embodiment of the invention, the connection means comprise at least one rod-like fastening arrangement. This is preferably a threaded bolt. It is also conceivable, however, to have, for example, a rod-like fastening arrangement such as a threaded rod. By means of a rod-like arrangement, the individual functional groups can be connected to one another so as to be essentially stress-free. Furthermore, the rod-like fastening arrangement may also be used in a simple way for fastening the device according to the invention to an actuator carrier, a cylinder head or the like. However, other devices which seem appropriate to a person skilled in the art and by means of which the functional groups can be connected to one another and fixed are also suitable as connection means.
The armature housing is advantageously of frame-like design, and it serves for mounting the at least one pivoting armature. Such a configuration of the armature housing provides for a reliable and protected receptacle for the pivoting armature, and engagement points for the rod-like arrangement for connecting the functional groups can be introduced into the receptacle in a simple way.
The second and/or the third functional group may correspondingly comprise a first or a second receptacle device which are of essentially frame-like design. The armature housing and the receiving device may for example be welded together from individual parts or may be cast. They are expediently configured in such a way that they are provided in each case with stiffening means. For example, the receiving devices each comprise a main frame and a side frame, between which the respective electromagnetic unit is fastened and, if appropriate, one or more rigid flexion beams attached to the end face. The receiving devices thus form reliable and dimensionally stable receptacles for the respective electromagnetic unit.
The connection means expediently are connected to the frame-like receptacle for the first and/or the second functional group. In particular the functional groups may be braced, via at least one connection means in the form of a threaded bolt, in such a way that the latter extends into a bore of the two frame-like receptacles and a bore of the frame-like armature housing.
The device according to the invention can be adjusted particularly effectively when the active surfaces of the first and of the second electromagnetic unit are oriented in parallel. In this case, the frame-like receptacles for the electromagnetic units and the armature housing are expediently oriented essentially in parallel.
Particularly when the active surfaces of the electromagnetic units are oriented in parallel, it is advantageous if the pivoting armature is wedge-shaped. This ensures that the active surface of the electromagnetic unit and the respective active surface of the pivoting armature, when the latter is pivoted towards this electromagnetic unit, are oriented essentially in parallel, so that a minimal holding power has to be applied. In particular, in this case, the machining of the active surfaces before the connection of the functional groups may be carried out in such a way that, first, the functional group comprising an electromagnetic unit is placed onto the functional group comprising the pivoting armature and, then, an electromagnetic unit is energized, so that the pivoting armature is pulled up by a yoke, for example the valve opening yoke of the electromagnetic unit. An erosive medium is then introduced between the pivoting armature and the yoke and the two functional groups are moved in an oscillating motion relative to one another essentially parallel to the active surfaces. The second active surface of the pivoting armature and the active surfaces of the yoke, for example the valve closing yoke assigned to the second electromagnetic unit, are thereafter treated in a corresponding way.
The device according to the invention may be designed as a double actuator, so that it can serve for a simultaneous actuation of two gas exchange valves.
The invention will become more readily apparent from the following description of exemplary embodiments of the device according to the invention on the basis of the accompanying drawings.